Feasibility Study on a Multi-Channeled Seismometer System with Phase-Shifted Optical Interferometry for Volcanological Observations
Tomoki Tsutsui*,, Yoshiharu Hirayama**, Toshiharu Ikeda**, Keiji Takeuchi**, and Hiroshi Ando**
*Sakurajima Volcano Research Center (SVRC), Disaster Prevention Research Institute (DPRI), Kyoto University
1722-19 Sakurajimayokoyama-cho, Kagoshima 891-1419, Japan
**Hakusan Corporation, Tokyo, Japan
A new Phase-Shifted Optical Interferometry seismometer system was tested in terms of its feasibility for multi-channeled volcanological observations in two volcanos in Japan. The system is capable of both sensing ground motions and transferring its signals through optical means. The prototype of this system comprises three optical-wired stations and optical components, and was deployed in Sakurajima Volcano in 2016 and in Asama Volcano in 2017. The system successfully operated for 134 days in total and provided seismograms that are in good agreement with those obtained using conventional systems. Several obstacles for putting this system to practical use that need to be solved were found through tests. Their solutions will be explored in subsequent research.
-  S. Matsumoto, H. Shimizu et al., “Short-term spatial change in a volcanic tremor source during the 2011 Kirishima eruption,” Earth, Planets and Space, Vol.65, pp. 323-329, 2013.
-  T. Tsutsui, M. Iguchi et al., “Structural evolution beneath Sakurajima Volcano, Japan, revealed through rounds of controlled seismic experiments,” J. Volcanol. Geotherm. Res., Vol.315, pp. 1-14, doi: 10.1016/j.jvolgeores.2016.02.008, 2016.
-  S. M. Hansen, B. Schmandt et al., “Seismic evidence for a cold serpentinized mantle wedge beneath Mount St Helens,” Nat. Commun., Vol.7, p. 13242, doi: 10.1038/ncomms13242, 2016.
-  M. Zumberge, J. Berger et al., “An optical seismometer without force feedback,” Bull. Seism. Soc. Am. Vol.100, No.2, p. 598, 2010.
-  J. Berger, P. Davis et al., “Performance of an optical seismometer from 1 μHz to 10 Hz,” Bull. Seism. Soc. Am., Vol.104, No.5, p. 2422, 2014.
-  A. Araya, “Wideband Short-Period Seismometer using a Laser Interferometer,” Tech. Res. Rep. (ERI, Univ. Tokyo), Vol.1, No.1, 1996 (in Japanese).
-  M. Yoshida, Y. Hirayama et al., “Real-time displacement measurement system using phase-shifted optical pulse interferometry: Application to a seismic observation system,” Japanese J. of Applied Physics, Vol.55, Article No.022701, 2016.
-  H. Nakstad and J. T. Kringlebotn, “Realisation of a full-scale fibre optic ocean bottom seismic system,” Proc. of 19th Int. Conf. on Optical Fibre Sensors, Vol.7004, 700436, doi:10.1117/12.791158, 2008.
-  J. T. Kringlebotn, H. Nakstad et al., “Fibre optic ocean bottom seismic cable system: from innovation to commercial success,” Proc. of 20th Int. Conf. on Optical Fibre Sensors, Vol.7503, 75037U, doi:10.1117/12.837636, 2008.
-  H. Y. Au, S. K. Khijwania et al., “Fiber Bragg grating based accelerometer,” Proc. 19th Int. Conf. on Optical Fibre Sensors, Vol.7004, doi:10.1117/12.785992, 2008.
-  K. Hotate, M. Enyama et al., “A multiplexing technique for fibre Bragg grating sensors with the same reflection wavelength by the synthesis of optical coherence function,” Meas. Sci. Technol., Vol.15, No.1, p. 148, 2004.
-  Y. Hasada, J. Kasahara et al., “Confirmation of physical quantity of DAS (Distributed Acoustic Sensor) measurements in comparison to seismometers,” Proc. of the 138th SEGJ Conf., 2018.
-  J. Kasahara, Y. Hasada et al., “Evaluation of time lapse of the near-surface layer due to precipitation,” Proc. of the 138th SEGJ Conf., 2018.
-  Japan Meteorological Agency, “The Seismological Bulletin of Japan,” http://www.data.jma.go.jp/svd/eqev/data/daily_map/index.html, 2017 [accessed May 14, 2019]
-  T. Minakami, “Fundamental research for predicting volcanic eruptions Part 1,” Bull. Earthq. Res, Inst. Univ. Tokyo, Vol.38, pp. 497-544, 1960.
-  K. Kamo, T. Furuzawa et al., “Some natures of volcanic micro-tremors at the Sakura-jima Volcano,” Bulletin of the Volcanological Society of Japan, 2nd Series, Vol.22, pp. 41-58, 1977.
-  M. Iguchi, “Distribution of The initial motions of volcanic microearthquakes (B-Type) at Sakurajima Volcano,” Annuals, Disas, Prev. Res. Inst., Kyoto Univ., No.32-1, pp. 13-22, 1989.
-  S. Mariyanto, M. Iguchi et al., “Constraints on the source mechanism of harmonic tremors based on seismological, ground deformation, and visual observations at Sakurajima volcano, Japan.,” J. Volcanol. Geotherm. Res., Vol.170, pp. 198-217, 2008.
-  M. T. Tarner and F. Koehler, “Velocity spectra – digital computer derivation and applications of velocity functions,” Geophys., Vol.39, pp. 859-881, 1969.
-  Y. Aoki, M. Takeo et al., “P-wave velocity structure beneath Asama Volcano, Japan, inferred from active source seismic experiment,” J. Volcanol. Geotherm. Res., Vol.187, pp. 272-277, doi: 10.1016/j.jvolgeores.2009.09.004, 2009.